Modeling the temporal dynamics of intertidal benthic infauna biomass with environmental factors: Impact assessment of land reclamation

Abstract

Anthropogenic activities such as land reclamation are threatening tidal marshes worldwide. This study's hypothesis is that land reclamation in a semi-enclosed bay alters the seasonal dynamics of intertidal benthic infauna, which is a key component in the tidal marsh ecosystem. Mai Po Tidal Marsh, Deep Bay, Pearl River Estuary, China was used as a case study to evaluate the hypothesis. Ecological models that simulate benthic biomass dynamics with governing environmental factors were developed, and various scenario experiments were conducted to evaluate the impact of reclamations. Environmental variables, selected from the areas of hydrodynamics, meteorology, and water quality based on correlation analysis, were used to generate Bayesian regression models for biomass prediction. The best-performing model, which considered average water age (i.e., a hydrodynamic indicator of estuarine circulation) in the previous month, salinity variation (i.e., standard deviation of salinity), and the total sunny period in the current month, captured well both seasonal and yearly trends in the benthic infauna observations from 2002 to 2008. This model was then used to simulate biomass dynamics with varying inputs of water age and salinity variation from coastal numerical models of different reclamation scenarios. The simulation results suggest that the reclamation in 2007 decreased the spatial and annual average benthic infauna biomass in the tidal marsh by 20%, which agreed with the 28% biomass decrease recorded by field survey. The range of biomass seasonal variation also decreased significantly from 2.1 to 230.5g/m² (without any reclamation) to 1.2 to 131.1g/m² (after the 2007 reclamation), which further demonstrates the substantial ecological impact of reclamation. The ecological model developed in this study could simulate seasonal biomass dynamics and evaluate the ecological impact of reclamation projects. It can therefore be applied to evaluate the ecological impact of coastal engineering projects for tidal marsh management, conservation, and restoration.

Keywords: Bayesian regression model; Benthic infauna; Land reclamation; Pearl River Estuary; Water age.